PROJECT SUMMARY/ABSTRACT The SWOG Statistical Center in Seattle, Washington, served as the coordinating center for two large prostate cancer prevention trials: The Selenium and Vitamin E Cancer Prevention Trial (SELECT) and the Prostate Cancer Prevention Trial (PCPT). SELECT was a Phase III, double-blind, placebo-controlled study designed to assess the effect of selenium and vitamin E, alone and in combination, primarily on prostate cancer incidence and secondarily on other cancer incidence. SELECT randomized 35,533 men between 2001 and 2004. PCPT, also a Phase III, double-blind trial, randomized 18,882 men to either finasteride or placebo between 1994 and 1997. Although schedules and requirements varied between the two studies, substantial serum, plasma, white blood cells, and prostate tissue were collected on both, resulting in rich biorepositories. Each had extensive prospective data collections which included diet and dietary supplements, quality of life, physical activity, medications, other cancer diagnoses, cardiovascular endpoints, and treatment adverse events. Although there have been significant scientific collaborations to date, there remain numerous opportunities to further interrogate the clinical database and biobanks. Additionally, serum and plasma measures and extensive genotyping data have already been obtained and are available for other investigators to use. These cohorts are fully mature with 6,045 deaths and median follow-up of 18.4 years on PCPT and 3,762 deaths and median follow-up of 10.1 years on SELECT. There have been 2,401 and 2,475 prostate cancers detected during the trials plus an additional 890 and 338 prostate cancers identified via Medicare linkage in PCPT and SELECT, respectively. Other primary cancers have also been documented either during the trials or through data linkage. In addition to being able to extend the results of these well-conducted, randomized clinical trials through linkages to Medicare, NDI and completed GWAS studies, these data can be used for epidemiologic research as part of the ongoing consortium projects. We request funds to continue to enrich the cohorts by collecting new data elements such as end point data from Medicare and National Death Index linkages. We plan to update our linkages early in the upcoming grant period. We also request support for the cohort team to develop detailed documentation and data sets to load into the Cancer Epidemiology Data Repository, and we ask for continued support to provide a stable infrastructure for the PCPT serum and PCPT and SELECT tissue repositories (all located at the University of Colorado). With continued funding for the Statistical Center and some of our key scientific colleagues, we will be able to provide administrative assistance and expertise to investigators who apply for additional funding to conduct studies using our rich biologic repositories and clinical databases from PCPT and SELECT.